Not a silly question at all, depending on why you are interested in NSA or sugar-free desserts.
NSA (No sugar added) products can, and often do, contain things like honey, maltose, dextrose, fructose, or other things which are processed in the body much like sucrose (table sugar). The apple pie example earlier is a good one - there is definitely 'natural' sugar (fructose) in the apples in that pie, even if the baker did not add granulated sugar to the recipe. It is even legal (but not nice) for a food containing turbinado to be labeled 'NSA' - turbinado being more commonly known as 'raw' sugar and being processed in the body
exactly like its granulated white sister. I haven't seen this happen yet in anything I've come across at WDW, but it is still feasible. They do have many NSA things that contain fruit or have crusts which will process in the body like sugar.
Sugar-free items are generally sweetened with artificial sweeteners like sucralose (Splenda), aspartame (Equal/Nutrasweet), or saccharine (Sweet-n-Low) and will often have little or no effect on blood sugar since these things are not processed like sugar in the body.
HTH